Coolant in no.1 cyl causing miss

[Rays74]

Hi all,

My '74 620's L18 has begun doing a strange thing .......... in the morning and sometimes upon restart after an hour or so the engine will miss and run on 3 cyl for approx 5-10secs then clear up and run fine. I rebuilt this engine 6 years ago and for the last 30k has run great with no oil or coolant probs. I pulled the plugs (all look same nice latte coloring) and did a compression check and they are all within 5psi of eachother (150-155.... I used L20B pistons in the build, a little lower comp but runs great). There is no water in the oil or viseyversey.

No.1 piston top does have the classic steam cleaned look when viewed through the plug hole.

 

Some years ago I DID have a coolant and oil mixing problem in my 510 wagon which turned out to be a cracked A87 head so I'm worried this may be a repeat..lol.

 

Anyone ever encounter this ?

thanks,

-Ray

[datzenmike]

Do you have to top up the coolant often or at all? At worst it may be the head gasket is going.

 

A Hail Mary might be to re-torque your head bolts. Loosen ONE AT A TIME and tighten to 60 ft lbs. Then move to the next bolt, any order you like. May not help but cheap and easy to try.

[Rustbin]

I had coolant in number one cylinder once, ended up hydro locking and broke a head bolt. I'm not sure if it was the head gasket or what but that was 20 something years ago and I still haven't fixed it yet.

[banzai510(hainz)]

I would make sure the intake is tight if loose at that area is coul suck water in thru the water passage from intake manifold.

[Stoffregen Motorsports]

Yes, check the intake manifold. If it persists, try removing the spark plugs after is sits for and hour or so, but before you crank it to start. If coolant is seeping in, that's goingto be when you see it.

 

I don't think that's the issue though because if it did seep after it warmed up, sitting overnight would allow more coolant seepage and it would miss upon first cold start too.

 

When's the last time you replaced your plug wires?

[datzenmike]

Coolant milkiness in oil: Water won't directly get into oil because all oil passages are under 50 PSI. Never seen the copper ring on a head gasket leak. Mechanics will tell you anything if they can't figure out what the real cause is so they can sell you something or do more work.

 

Head gasket failure, water seeps into combustion chamber, turned to steam, some squeezes past rings gets into oil pan.

Head gasket failure, water seeps into the oil drain back hole at back of head. Possible, very unlikely.

Water pump has eroded a hole in the back of the timing cover, water gets into oil pan.

 

 

[Rays74]

Thanks for the replies.....once in a while I do top up the coolant but it's not often and less than a pint when done, I will redo the head bolts just to rule it out.

 

This is def a problem after it's set overnight as well as after sitting in between errands and such, I hadn't thought of the intake or it's gasket so I will def check that. I have seen moisture in that cyl overnight once I figured out what cylinder was affected and pulled it's plug, I did swap entire ignitons from my other truck just to rule out the EI dizzy being a problem...no change of course.

 

In the the other car I mentioned (72 wagon with L16) the milkiness was only in the radiator.... I had never encountered this (I'm an M/C tech) but it finally ended up being the head that was the problem (A87 peanut, I bought the eng complete from Datsun parts so yeah) as I bolted on a std 210 head and the problem went away (25k ago). The radiator full of that mixture but not the crankcase was a head scratcher! LOL

_Ray 

[Stoffregen Motorsports]

Be sure to release the pressure in the radiator before re-torquing the head bolts.

[datzenmike]

Forgot to mention. Only re-torque head bolts when the engine is cold from sitting over night. If you do one bolt at a time you don't have to worry about draining any coolant.